package Q104;

import java.util.LinkedList;
import java.util.Queue;

/**
 * 二叉树的最大深度
 *
 * @author 23737
 * @time 2021.11.25
 */
public class Test {
    public static void main(String[] args) {

    }
}

class TreeNode {
    int val;
    TreeNode left;
    TreeNode right;

    TreeNode() {
    }

    TreeNode(int val) {
        this.val = val;
    }

    TreeNode(int val, TreeNode left, TreeNode right) {
        this.val = val;
        this.left = left;
        this.right = right;
    }
}

/**
 * 层序遍历
 */
class Solution {
    public int maxDepth(TreeNode root) {
        if (root == null) return 0;
        Queue<TreeNode> queue = new LinkedList<>();
        queue.add(root);
        int res = 0;
        while (!queue.isEmpty()) {
            res++;
            int n = queue.size();
            for (int i = 0; i < n; i++) {
                TreeNode node = queue.poll();
                if (node.left != null) queue.add(node.left);
                if (node.right != null) queue.add(node.right);
            }
        }
        return res;
    }
}

/**
 * dfs
 */
class Solution2 {
    public int maxDepth(TreeNode root) {
        if (root == null) {
            return 0;
        }
        int leftDepth = maxDepth(root.left);
        int rightDepth = maxDepth(root.right);
        return Math.max(leftDepth, rightDepth) + 1;
    }
}